Cannot access settings, display settings or extensions (nothing happens)

Cannot access "settings" (right click desktop), "display settings" (right click desktop) or "extensions" (through Arc menu), nothing happens. But I can access "extension manager" for example (self-installed) and other apps. No error, only clicking troubleshot, no command line troubleshooting (don't know where to start).
It started ~4 updates ago (not recent). Any help appreciated.

This sounds like nautilus-desktop is not managing the desktop. You might try

sudo apt install --reinstall zorin-os-desktop

Have you ever installed a different desktop environment or file manager on Zorin OS?

Thanks, since "Arc Menu" was not giving error messages I re-enabled "Zorin Menu" and it told me something LIKE "... gnome-control-center". Did a search online to install/reinstall and installed! Immediately got update notifications, for missing software, installed updates and rebooted. Thanks again.

Yes, I installed the Dolphin (KDE), thanks again.